Field of the Invention
The present invention relates to a solenoid drive device which drives a solenoid that acts as an inductance load.
Description of the Related Art
With a fuel injection device (injector) that injects fuel directly into the interior of a cylinder of an engine, a valve-open state of the injector is brought about by imposing a high voltage on a solenoid, which acts as an inductance load, and causing a large electric current to flow therein, and thereafter, the valve-open state is maintained by having a small holding electric current flow to the solenoid. In this case, a power source voltage is boosted and a high voltage (boost voltage) is generated by a boost voltage power source means such as a DC-DC converter or the like, and the injector is placed in a valve-open state by applying the boost voltage to the solenoid.
In Japanese Patent No. 4343380, there is disclosed the feature of limiting a value of the boost voltage (voltage value of a capacitor) to be less than or equal to a predetermined voltage value, by connecting a constant voltage diode as a voltage limiting means in parallel with respect to a high voltage charging capacitor that makes up the DC-DC converter.